Terminal point of a repeated reduction of usigma starting at 2^n.

Terms

a(0) =1a(1) =6a(2) =20a(3) =72a(4) =72a(5) =72a(6) =20a(7) =72a(8) =72a(9) =17280a(10) =4800a(11) =17280a(12) =72a(13) =17280a(14) =1152000a(15) =5184a(16) =5184a(17) =5184a(18) =96000a(19) =5184a(20) =345600a(21) =1244160a(22) =320000a(23) =1244160a(24) =82944000a(25) =89579520a(26) =71663616000a(27) =298598400a(28) =1244160a(29) =82944000